The title of the patent reads A grant to Thomas Savery

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[22] "Experimental Philosophy," vol. ii., p. 465.

The most important advance in actual construction, therefore, was made by Thomas Savery. The constant and embarrassing expense, and the engineering difficulties presented by the necessity of keeping the British mines, and particularly the deep pits of Cornwall, free from water, and the failure of every attempt previously made to provide effective and economical pumping-machinery, were noted by Savery, who, July 25, 1698, patented the design of the first engine which was ever actually employed in this work. A working-model was submitted to the Royal Society of London in 1699, and successful experiments were made with it. Savery spent a considerable time in planning his engine and in perfecting it, and states that he expended large sums of money upon it.

Having finally succeeded in satisfying himself with its operation, he exhibited a model "Fire-Engine," as it was called in those days, before King William III. and his court, at Hampton Court, in 1698, and obtained his patent without delay. The title of the patent reads: "A grant to Thomas Savery, Gentl., of the sole exercise of a new invention by him invented, for raising of water, and occasioning motion to all sorts of mill-works, by the impellant force of fire, which will be of great use for draining mines, serving towns with water, and for the working of all sorts of mills, when they have not the benefit of water nor constant winds; to hold for 14 years; with usual clauses."

Savery now went about the work of introducing his invention in a way which is in marked contrast with that usually adopted by the inventors of that time. He commenced a systematic and successful system of advertisement, and lost no opportunity of making his plans not merely known, but well understood, even in matters of detail. The Royal Society was then fully organized, and at one of its meetings he obtained permission to appear with his model "fire-engine" and to explain its operation; and, as the minutes read, "Mr. Savery entertained the Society with showing his engine to raise water by the force of fire. He was thanked for showing the experiment, which succeeded, according to expectation, and was approved of." He presented to the Society a drawing and specifications of his machine, and "The Transactions"[23] contain a copperplate engraving and the description of his model. It consisted of a furnace, _A_, heating a boiler, _B_, which was connected by pipes, _C C_, with two copper receivers, _D D_. There were led from the bottom of these receivers branch pipes, _F F_, which turned upward, and were united to form a rising main, or "forcing-pipe," _G_. From the top of each receiver was led a pipe, which was turned downward, and these pipes united to form a suction-pipe, which was led down to the bottom of the well or reservoir from which the water was to be drawn. The maximum lift allowable was stated at 24 feet.

The engine was worked as follows: Steam is raised in the boiler, _B_, and a cock, _C_, being opened, a receiver, _D_, is filled with steam. Closing the cock, _C_, the steam condensing in the receiver, a vacuum is created, and the pressure of the atmosphere forces the water up, through the supply-pipe, from the well into the receiver. Opening the cock, _C_, again, the check-valve in the suction-pipe at _E_ closes, the steam drives the water out through the forcing-pipe, _G_, the clack-valve, _E_, on that pipe opening before it, and the liquid is expelled from the top of the pipe. The valve, _C_, is again closed; the steam again condenses, and the engine is worked as before. While one of the two receivers is discharging, the other is filling, as in the machine of the Marquis of Worcester, and thus the steam is drawn from the boiler with tolerable regularity, and the expulsion of water takes place with similar uniformity, the two systems of receivers and pipes being worked alternately by the single boiler.